At present, the diffusion transfer processes are well known in the art, and details thereof are described in A. Rott and E. Weyde, Photographic Silver Halide Diffusion Process, Focal Press, London (1972); J. Stutge, V. Walworth and A. Shepp, Imaging Processes and Materials: Neblette's Eighth Edition, Chapter 6, Instant Photography and Related Reprographic Processes, Van Nostrand Reinhold (1989); and G. Haist, Modern Photographic Processing, Vol. 2, Chapter 8, Diffusion Transfer, John Wiley and Sons (1979).
According to these diffusion transfer processes, many kinds of photographic materials can be prepared. As an example, a photosensitive element in which a silver halide emulsion is applied to a support and an image receiving element in which an image receiving layer containing silver precipitating nuclei is applied to another support are superimposed on each other, and an alkali processing composition which is a processing element, such as a high viscosity or low viscosity alkaline processing composition containing a developing agent and a solvent for a silver halide, is developed between the above-described two elements, whereby a transferred image can be obtained.
In the silver salt diffusion transfer processes, acquisition of transferred images for a shorter period of time has recently become an important problem for simplifying handling. For solving this problem, it is a primary subject to accelerate developing reaction in a photosensitive element and an image receiving sheet.
Use of hydroxylamine compounds as developing agents has been known in the silver salt diffusion transfer processes. Such hydroxylamine compounds are described in U.S. Pat. Nos. 2,843,481, 2,857,274, 2,857,275, 2,857,276, 3,287,124, 3,287,125, 3,293,034, 3,362,961, 3,455,916, 3,467,711 and 3,619,185, JP-B-48-30499 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-48-43937 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-49-88521, etc. These hydroxylamine compounds have the advantage that colored matter is difficult to be formed when they remain in prints, but are low in developing speed, resulting in insufficiency for completing developing reaction for a shorter period of time. For this reason, in order to increase the developing speed, use of 3-pyrazolidinone compounds in combination with the above-mentioned hydroxylamine compounds is described in JP-B-49-13580, etc. It is described in many literatures of photochemistry that use of the 3-pyrazolidinone compounds as superadditive developing agents (or supplementary developing agents) in combination with other developing agents increases the developing speed. This is also a very effective means in the silver salt diffusion transfer processes. However, studies conducted by the present inventors have proved that the 3-pyrazolidinone compounds have the disadvantage that when they remain in prints, oxidation intermediates thereof oxidize silver images, thereby fading the silver images. That is, the 3-pyrazolidinone compounds show the different behavior from that of the above-mentioned hydroxylamine compounds. Further, the disadvantage is also known that coloring of the oxidation intermediates themselves causes stains. In the silver salt diffusion transfer processes in which the processing solution compositions are developed between the photosensitive elements and the image receiving elements, followed by separation of the image receiving elements to obtain prints of silver images, the 3-pyrazolidinone compounds naturally remain in the prints and the oxidation intermediates are formed by air oxidation. As a result, in the silver salt diffusion transfer processes using the processing compositions containing the 3-pyrazolidinone compounds, the problem has been revealed that the silver images are particularly liable to fade, and it has become an important subject to solve this problem.